1. Field of the Invention
The present invention relates to a double color injection machine with a shaft and a disc, especially to a double color injection machine that provides fast and precise positioning without affecting respective rotation of the shaft and the disc. By the design of the shaft sleeve on the shaft corresponding to the first bearing of the disc, friction and wear are minimized, manufacturing cost is reduce and assembly efficiency is improved.
2. Description of Related Art
Generally, double color injection molding means to produce products with two colors on the appearance or with double materials by using two colors of plastic or two kinds of materials. As to a double color injection molding machine, it is disposed with two sets of molds. A female die of the mold is connected to two material feeding units movably and respectively. A male die of the mold is fixed on two opposite surfaces of a mold plate that moves from an initial orientation to the opposite (at 180 degrees) and then rotates back to the original position. The male die and the female die are joined, then material is feeding and the mold is opened. Next the mold plate is rotated 180 degrees and turned to the opposite so as to change the position of the male die. The male die and the female die are joined again and material is feeding the second time. Then open and release the mold to get double-color or double-material products. The double color molding machine is divided into different designs according to basic design and molding products. The rotatable mold template includes two designs, one is with a shaft (shaft-type) and the other is with a disc (disc-type).
The disc-type double color injection molding machine uses motor to rotate the disc and change the positions of the two sets of molds. The positioning is achieved by a positioning pin and a positioning slot on molds. However, such positioning way has a shortcoming. After long term use, the positioning pin has wear or the positioning slot is enlarged. This leads to imprecise positioning.
Refer to U.S. Pat. No. 8,066,507, a horizontal injection molding machine includes a rotary plate that includes a rotary shaft extending in a horizontal direction and can be mounted with a plurality of molds and a stationary base that includes a bearing supporting the rotary shaft of the rotary plate in a cantilever manner and a rotary drive device of the rotary plate. The horizontal injection molding machine features on that the rotary plate is formed into a disk shape and is supported by the stationary base. The stationary base is disposed with a power source to position the rotary backwards. A disc spring in the rotary plate is used for buffering. However, such positioning is not precise.
Moreover, in the shaft-type double color injection molding machine, a gearing around a shaft is driven by a rack so as to turn a mold fixed on the shaft to the opposite. The positioning way is achieved according to the teeth of the gearing engaged with the rack. However, a gear backlash causes problems between the mating components. Thus the positioning is also not precise.
In order to overcome shortcomings of the shaft-type or disc-type injection molding machines, an integrated type machine has been developed. Refer to Taiwanese Pub. No. M337467, a disc-type injection molding machine that is able to be mounted with a shaft is revealed. A shaft can be assembled on or removed from the injection molding machine. The disc-type injection molding machine includes a main body with a base wall, a tube unit, a disc, a disc drive mechanism, and a shaft drive mechanism. The base wall is disposed with a mounting hole. The tube unit consists of a disc mounting tube that is rotatably assembled on the mounting hole, a shaft mounting tube that is rotatably mounted in a first shaft channel of the disc mounting tube and a shaft driving rod that is reciprocally moved in a working direction and is inserted through a second shaft channel of the disc mounting tube. The shaft is connected to and moved with the shaft driving rod. The disc is linked to and assembled on the disc mounting tube. The disc drive mechanism is installed on the man body and used to drive the disc rotate a certain angle. The shaft drive mechanism is also disposed on the main body and used to drive the shaft driving rod to move reciprocally in a working direction and rotate a certain angle. In a turning cylinder of the shaft drive mechanism, the shaft is driven and rotated by a rack. The design also has the gear backlash problem. Moreover, the shaft and the disc are rotated relatively by means of the shaft mounting tube, the disc mounting tube and bearings. The structure is quite complicated. Thus the cost is increased and the assembly is time-consuming.